Both woven and non-woven fiber mats employing carbon fibers have been fabricated in the past for a variety of purposes such as in the electromagnetic interference (EMI) shielding of radios in automobiles. One of such known prior art product and method of manufacture thereof, is described in an article entitled "Conductive Fiber Mats as EMI Shield for SMC" (sheet molding compounds), by J. R. Quick and Z. Mate appearing in "Modern Plastics" --published May, 1982, pages 68-71. In this article, a number of SMC products employing panels molded from non-woven carbon fiber mats is described wherein the non-woven carbon fiber mats employ either 100% carbon fibers, 50% carbon fiber and 50% glass or 33% carbon fiber and 67% glass fiber in their makeup. Similar arrangements are also known in the art wherein the fabric being formed is woven by known weaving techniques, knitting or the like employing varying percentages of carbon fiber filament and glass fiber filaments. From one of the tables included in the article it is clear that the electrical surface resistance measured in ohms per square increases with decreasing carbon filament content and increasing glass fiber filament content. However, this method of interspersing glass filaments with carbon filaments to control the resulting surface resistance of the resulting sheet product at best can only achieve stepped increases in the resistance. As is well known to those skilled in the art, the surface resistivity of a product is in inverse relationship to its conductivity. Thus, where it is desired to finely control the electrical resistivity (conductivity) of a given sheet product, the technique of interspersing glass fiber filaments with conductive filaments of either carbon, aluminum or the like to achieve a desired resistivity (conductivity) is at best a gross technique requiring much experimentation and adjustment and more often than not resulting in a product having less than optimum values of electrical resistivity (conductivity) which are not uniformly dispersed within the sheet. To overcome this problem, the present invention was made.